A sure thing to have because if its older you don't want anti freeze going through the seal and having fun with your oil. The crank seals seal the case, one side from outside air and the otherside from the oil. so if one leaks your mixture will be really rich or really lean and if you don't know you'll seize your rod and won't be riding for a while. BUT if it happens, bore the jug get a wiseco crank,rod, and piston kit.- later